The dnaA protein is suspected to play an important role in the control of replication of the E. coli chromosome. Using bacteria containing the dnaA gene under lac control cloned in the high copy number plasmid pBR322 and plasmids in which the lacZ gene is cloned under dnaA control, I propose to determine the relationship between the intracellular concentration of the dnaA protein and initiation of replication of the E. coli chromosome and of the dnaA-dependent plasmid pSC101, as well as the expression of the presumably auto-regulated dnaA gene itself. As part of this study, I plan to develop a quantitative assay of plasmit DNA that employs HPLC chromatography for separation and UV absorbance for detection.